Hi heya and welcome back!
Although I am sorry it is due to having an unpleasant episode.
It sounds like a dip in blood sugar to me. Did you have an empty stomach at the time? Or maybe an earlier snack that was sugary/simple carb that could make your BGL (blood glucose level) spike and then plummet?
The physical exercise of washing your car likely contributed to the quick drop. Low blood sugar can mimic the feelings of a panic attack, and actually trigger one...and then the physical symptoms really take off on you!
Try to eat protein, complex carbs/whole grains and foods that sustain steady BGL's and that should prevent any future feelings like you described.
S.C.